Photoflash lamp primer composition

ABSTRACT

A miniature high performance flashlamp is disclosed which includes an improved primer material that is more stable in handling during lamp manufacture and further improves performance of the lamp in operation. Said primer material comprises a mixture in percentages by weight of 1-5% sodium chlorate, 1-6% sodium perchlorate, and the balance being zirconium, which mixture can be bonded to form a unitary mass with a polyvinyl pyrrolidone binder. An aqueous solution of the primer material which includes the polyvinyl pyrrolidone binder remains substantially gel-free for long time periods and provides a tough and adherent coating in the lamp.

[ Oct. 21, 1975 PHOTOFLASH LAMP PRIMER COMPOSITION- [75] Inventor:Vaughn C. Sterling, Cleveland, Ohio [73] Assignee: General ElectricCompany,

Schenectady, NY.

[22] Filed: July 11, 1974 [21] Appl. No.2 487,776

Related US. Application Data [62] Division of Ser. No. 315,663, Dec. 15,I972.

[52] US. Cl. 149/40; 149/42; 149/44;

149/83; 149/85 [51] Int. Cl. C06B 33/12 [58] Field of Search 149/40, 42,44, 85, 83

[56] References Cited UNITED STATES PATENTS 3,724,990 4/l973 Schupp149/40 X Primary Examiner-Stephen J. Lechert, Jr. Attorney, Agent, orFirm-John F. McDevitt; Lawrence R. Kempton; Frank L. Neuhauser [57]ABSTRACT A miniature high performance flashlamp is disclosed whichincludes an improved primer material that is more stable in handlingduring lamp manufacture and further improves performance of the lamp inoperation. Said primer material comprises a mixture in percentages byweight of l-5% sodium chlorate, 1-6% sodium perchlorate, and the balancebeing zirconium, which mixture can be bonded to form a unitary mass witha polyvinyl pyrrolidone binder. An aqueous solution of the primermaterial which includes the polyvinyl pyrrolidone binder remainssubstantially gel-free for long time periods and provides a tough andadherent coating in the lamp.

2 Claims, 1 Drawing Figure US. Patent Oct. 21, 1975 BACKGROUND OF THEINVENTION velope to form a hermetic seal with a pair of electricallead-in wires having a metal resistance filament connected therebetween.In such electrical-ignition type photoflash lamps in general use atpresent, the inner ends of these lead-in wires are coated with a chargeof heat sensitive primer material so that when electrical current ispassed through the resistance filament there will be deflagration of theprimer material causing the shredded combustible foil in the lampenvelope to burn rapidly with incandescence.

With increasing miniaturization of a photoflash lamp such as thatdisclosed and claimed in U.S. Pat. No. 3,506,385 to Weber et al, andassigned to the assignee of the present invention, more difficulties areencountered with the primer material of the electrical-ignition systemboth as affects lamp manufacture and the lamp operation. Moreparticularly, a smaller bead size of the I oxidizing materials are alsogenerally not very soluble in the liquid coating compositions used toobtain the primer coatingon the in-leads, it further became neces-- saryto increase the oxidizer concentration even more so that enough oxidizerwas present throughout the v primer coating to cause complete combustionof the available fuel. The. percussion-sensitive nature of theseoxidizer substances makeshandling them hazardous so that it would bedesirable to reduce their concentration in the solid primer material.

, Certain primer materials are already known which can be applied ascoatings from a water-base suspension to reduce the hazards of handlingthe primer solids. A known primer material comprises a mixture inpercentages by weight of 4-50% phosphorus, 3-8% potassium chlorate, 630%potassium perchlorate, and

V the remainder beingtitanium which is described and claimed incopending patent application, Ser. No.

198,547 tiled Nov. 15,. 1971 in the name of Lewis J,

Schupp and assigned to the assignee of the present incomprises a mixturein percentages by weight of 4-50% phosphorus 10 2570 potassium chlorate,4-l0% sodium chlorate, and the remaining being titanium which isdescribed and claimed in pending application, Ser. No. 198,587, filedNov. 15, 1971 in the name of the same inventor and also assigned to theassignee of the present invention. The solid primer coating can also beapplied from an aqueous suspension containing the polyvinyl alcoholbinder.

SUMMARY OF THE INVENTION An improved primer material has now beendiscovered which can be applied reliably as a coating for the in-leadmembers of an electrical-ignition type flashlamp from a waterbasesuspension wherein all oxidizer constituents of the primer'material aredissolved in the liquid suspension. The present primer material exhibitsproper ignition sensitivity along with low blast characteristics uponactuation which makes it especially suitable for miniaturized photoflashlamps of the all-glass type which are described in the aforementionedU.S. Pat. No. 3,506,385. In such lamps having an internal volume ofapproximately 0.3-0.4 cubic centimeters it becomes possible to flash thelamps reliably with a high constant light output by using the presentprimer material at a primer weight range between 0.5 and 2.5 milligrams.Additionally, the lower ratio of oxidizer to fuel in the present primermaterial reduced the hazards of handling the primer solids.

An improved flashlamp construction of the present invention therebycomprises a hermetically sealed light-transmitting envelope, a quantityof filamentary combustible material distributed within said envelope, afilling of combustion-supporting gas in said envelope, and an electricalignition system in communication with the interior of said envelope,said electricalignition system including a quantity of primer materialwhich comprises an adhesively bonded solid mixture in percentages byweight of l-5% sodium chlorate, l-6% sodium perchlorate, and the balancebeing zirconium. The combined weight percent of sodium chlorate andsodium perchlorate in the primer mixture does not exceed ten percent inthe preferred compositions so that a water-base coating composition canbe used in applying the primer material having all of said oxidizersubstances completely dissolved in the coating composition. By havingthe oxidizer constituents fully dissolved in the coating compositionthere are a number of benefits which include eliminating oxidizersegregation, reducing any flocculation and lumping tendency in thecoating composition, and maintaining constancy of the oxidizer-fuelproportions throughout the life of the liquid coating composition. Thepresent primer mixture is adhesively bonded to the envelope member witha polyvinyl pyrrolidone binder instead of the polyvinyl alcohol binderemployed in the referenced primer formulations. Substitution of apolyvinyl pyrrolidone binder provides additional advantages of lesserfoam tendency, a more rewettable nature, and higher tolerance to thedissolved oxidizers in the coating composition than was experienced withpolyvinyl alcohol.

The coating compositions for the primer material of the presentinvention comprises a suspension of the aforementioned solid mixture inan aqueous solution of commercially available polyvinyl pyrrolidonewhich can have an average molecular weight in the range from40,000-160,000. Certain optional materials such as dispersants andpreservatives can be added to the coating compositions in minor amountincluding polyvinyl alcohol which improves the toughness and chipresistance of the final solid coating. In a preferred coatingcomposition, the powered zirconium fuel is suspended by mixing with acolloidal silica suspending agent in an aqueous solution containing upto approximately 1% polyvinyl alcohol binder until a uniform smoothdispersion has been obtained. The sodium chlo rate and sodiumperchlorate oxidizers are separately dissolved with a fungicide in anaqueous solution containing up to 20% polyvinyl pyrrolidone binder whichprovides safe handling of the ,oxidi'zer substances prior to mixing withthe liquid fuel suspension when the final coating composition is to beapplied. One part of said oxidizer solution can be added to about 56parts of said fuel suspension to provide the final coating composition.

BRIEF DESCRIPTION OF THE DRAWING 1 In the drawing, the single FIGURE isa crosssectional view partly in elevation of a preferred flashlamp ofthe present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawing, apreferred flashlamp, according to the invention comprises a glass bulbor envelope 1 which, as shown, may be formed of a short length of glasstubing, for example, about one-fourth outside diameter, which isconstricted and rounded off at one end as indicated at 2 and closed offthereat by an exhaust tip 3 and is formed at the other or base end 4with a stem press base. The lead-in wires 6 are sealed in oppositecorners 7 of the stem press base which provides a longer path length forthe in-leads through the lamp envelope and less likelihood of leakageand loss of the hermetic seal. The envelope 1 is preferable made of aborosilicate hard glass which is capable of forming a good hermetic sealto the preferred iron-nickel cobalt alloys employed for the in-leads 6.The preferred glass compositions consist essentially of the followingconstituents in about the range stated by weight: 60 to 75% SiO 10 to25% B 1 to 10% A1 0 4 to 10% total alkali oxides, and 0 to BaO exceptfor incidental impurities and residual fluxes and refining agents, andhaving a mean coefficient of linear thermal expansion between 0 and 300Cabout in the range of 40 to 50 X per C. The preferred alloys for atleast one electrical in-lead being hermetically sealed through saidglass wall include commercial products known by the names Kovar, Rodar,Therlo, Fernico I, Fernico II, Nicoseal, Nilok, Sealvac A and others.Generally, these are allows predominantly of iron, nickel and cobalt,and optionally contain manganese in amounts generally less than 1percent preferably less than 0.5 percent, along with incidentalimpurities. The general range of composition for such alloys is 27 to32% Ni, -14 to 19% Co, less than 1.0Mn, the balance iron, except forincidental impurities. The composition of Kovar, a suitable leadmaterial is about 54% Fe, 29% Ni, 17% Co; 0.5% Mn, O.2% Si, and 0.06% C.The inner ends of the leads are coated with the primer material 8 andhave an electrical filament 9 connecting them. This filament may be afine tungsten wire or preferably constructed of a 97% tungsten 3%rhenium alloy. A quantity of filamentary combustible material 10 such asa shredded foil of zirconium or hafnium, for example, is distributedwithin the interior space of the envelope 1 which also contains afilling of a suitable combustion-supporting gas such as oxygen generallyat high pressure in excess of several atmospheres.

The solid coating of primer material in the above embodiment can beapplied to the in-lead members as a stabilized aqueous suspension of thepresent invention in various known ways. For example, the in-leadmembers can be dipped into the aqueous slurry followed by drying in theair or with heat to remove the liquid and produce a solid adheredcoating having the desired characteristics previously described.Alternately, the aqueous slurry can be sprayed on the in-lead membersand thereafter processed to provide a solid coating exhibitingcomparable performance.

As an example of suitable coating compositions which are prepared asgenerally above described in two portions so as to maintain the oxidizerand fuel constituents separately until the final coating composition isto be applied, there is listed below a typical formulation together withpermissible variation in the individual constituents as follows:

For the above coating compositions approximately one part of theoxidizer solution can be added to about 56 parts of the liquid fuelsuspension in the manufacturing plant by conventional means to providethe primer coating composition. After mixing the individual por tions toproduce a smooth even blend of the constituents, there is obtained aliquid coating composition which is stable in storage up to one week.The zirconium fuel material should have a particle range from a finemesh size to a micron size to provide the final smooth and uniformprimer coating.

While the best mode of carrying out the present invention has been setforth above, it will be understood that additions, changes andmodifications may be made thereto without departing from the spirit andscope of the invention as defined in the appended claims. For example,it will be apparent that still other optional constituents can be addedto the liquid coating compositions if desired so long as in minor amountto modify the film-forming characteristics of the final solid coatingwhen necessary for a particular lamp construction. Likewise, it will beapparent that other electricalignition type flashlamp constructionsother than herein specifically disclosed can employ the primer materialsof the present invention. It is intended to limit the present invention,therefore, only the scope of the following claims.

What I claim as new and desire by Letters Patent of the United Statesis:

1. A stabilized liquid suspension of primer material which comprises anaqueous solution of polyvinyl pyrcontaining in weight percent 68-80%zirconium, 20-35% water, O-5% colloidal silica and 0-2% polyvinylalcohol with a liquid solution containing in weight percent 45-75%water, 5-25% sodium chlorate, 5-30% sodium perchlorate, and 5-20%polyvinyl pyrrolidone dissolved in said solution.

1. A STABILIZED LIQUID SUSPENSION OF PRIMER MATERIAL WHICH COMPRISES ANAQUEOUS SOLUTION OF POLYVINYL PYRROLIDONE BINDER HAVING SUSPENDEDTHEREIN A SOLID MIXTURE CONTAINING 1-5% SODIUM CHLORATE AND 1-6% SODIUMPERCHLORATE AS DISSOLVED SOLIDS IN SAID SOLUTION, AND THE BALANCE BEINGZIRCONIUM BY WEIGHT OG SAID SOLID MIXTURE.
 2. A PRIMER COATINGCOMPOSITION FOR A FLASH LAMP WHICH COMPRISES AN ADMIXTURE OF A LIQUIDSUSPENSION CONTAINING IN WEIGHT PERCENT 68-80% ZIRCONIUM, 20-35% WATER,0-5% COLLOIDAL SILICA AND 0-2% POLYVINYL ALCOHOL WITH A LIQUID SOLUTIONCONTAINING IN WEIGHT PERCENT 45-75% WATER, 5-25% SODIUM CHLORATE, 5-30%SODIUM PERCHLORATE, AND 5-20% POLYVINYL PYRROLIDONE DISSOLVED IN SAIDSOLUTION.